A:
There are those who suspect Wildflower Center volunteers are the culpable
and capable culprits. Yet, others think staff members play some, albeit small, role. You
can torture us with your plant questions, but we will never reveal the Green
Guru's secret identity.

Thursday - July 10, 2008

QUESTION:

I live in Oklahoma and my red tips have rust spots on leaves and some plants are losing leaves. This is a clay soil; can you give me any info. on how to solve this problem?

ANSWER:

For openers, the red-tip photinia is non-native to North America, originating in the Far East. At the Lady Bird Johnson Wildflower Center, we are committed to the planting, protection and propagation of plants native to North America. Native plants are recommended because they are adapted to an area's soil, rainfall, heat (or cold), and so require less water, less fertilizer, less maintenance. We're not saying that your plants are suffering because they're non-native, necessarily, but that choosing the right plant, in advance, can save you a lot of grief and probably money because of lost plants. Unfortunately, the red tip photinia has been widely overused because it is cheap, fast-growing and the red leaves in the Spring are quite attractive.

In this Mississippi State University Extension Service Red-tip Photinia Almost Eliminated, you will likely find out why your plants are not prospering. Here is a quote from this article:

"Red-tip is highly susceptible to the fungal pathogen known as Entomosporium that causes leaf spots and ultimately defoliation. The disease has all but eliminated Red-tip from the list of recommended shrubs for Southern landscapes. In fact, the disease is so widespread that one plant pathologist jokingly explained that there are two types of Red-tip, those that have the disease and those that are going to get it! So, even though newly planted Red-tip bushes may stay disease free for many years, ultimately they will succumb to the inevitable."

Cotton Root Rot is also responsible for the loss of many ornamental plants in clay soil, and photinias are especially vulnerable. An article by Lynn Rawe from the Texas A&M Home Horticulture site describes the symptoms. There is no cure.

We're sorry that we can't give you the name of a spray or fungicide that would cure these plants, but we're afraid there is no such panacea. If the seemingly inevitable happens, try replacing the plants with plants native to Oklahoma, and tolerant of clay soils. However, if the clay is very dense, there will probably be drainage problems for any replacement, as well. If and when the photinias die, remove them and dispose of them in such a way that whatever disease has killed them will not be readily able to spread to other plants. Then incorporate compost or other humus into the soil, digging and mixing it deeply, and raising the bed, again to improve drainage. Don't try to plant new shrubs until late Fall, so they won't suffer from heat shock. Mulch them with shredded hardwood mulch, which will help keep the roots cool (or warm) and, as it decomposes, add still more organic matter to the soil, and keep this mulching up.

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